A wealth of experimental evidence points to the importance of decreased mitochondrial function and increased oxidative stress in age-related neurodegenerative conditions such as Parkinson's Disease (PD). Dopamine- producing nerve cells in the midbrain region of PD patients exhibit both of these defects, and eventually die due to progressive accumulation of cellular damage. The studies outlined in this proposal are designed to assess the role of FoxO family transcription factors in protecting dopaminergic neurons from oxidative stress and mitochondrial dysfunction. FoxO factors are directly implicated in cellular longevity and stress resistance, suggesting that long-term maintenance of quiescent neurons is dependent upon continued FoxO activity during the aging process. To determine whether FoxO activity is required for survival of dopaminergic neurons, the mammalian FoxO genes (FoxO1, FoxO3 and FoxO4) will be simultaneously deleted from these cells in mice using conditional knockout technology. The effects of FoxO deletion will be tested in live mice using defined physiological assays to measure motor performance and striatal dopamine content (Aim 1), and in cultured primary neurons using a battery of assays to measure oxidative stress and mitochondrial function (Aim 2). Loss of FoxO factor expression is expected to cause progressive neuronal cell death in mice due to the accumulation of cellular damage from unrestrained oxidative stress and decreased mitochondrial energy production. PUBLIC HEALTH RELEVANCE: Because PD is the second most common neurodegenerative disorder and is increasing in incidence due to rising life-expectancy, research efforts aimed at elucidating the mechanisms that drive oxidative stress and mitochondrial dysfunction in PD will be required to develop improved therapies that reduce the burden of this neurological disease worldwide. The research proposed in this application therefore presents a novel mechanism to explain the etiology of PD, and may also provide a new mammalian model of PD that will be useful for development of future therapies.